Colorants, which include pigments and dyes, are used in a variety of personal care products. Titanium dioxide is commonly used as a pigment in liquid foundations, sunscreens and personal care products. However, titanium oxide has been prohibited in certain applications, such as aerosol application, due to health concerns.
Calcium carbonate is another pigment commonly used in personal care products. Currently, calcium carbonate is not prohibited in personal care products due to health concern. Calcium carbonate is therefore viewed as a potential replacement for titanium dioxide. However, due to calcium carbonate's hydrophilic nature, calcium carbonate is not easily incorporated into many personal care products such as liquid foundation formulations and aerosol personal care products, which include water. Calcium carbonate swells in the presence of water, resulting in clumping and agglomeration.
In order to render calcium carbonate useful in a wide-range of personal care products, it is desirable to modify calcium carbonate with a hydrophobic material. Current hydrophobic compounds which are used to modify pigments include lauroyl lysine, natural flower waxes and glutamate cysteine arginine. These compounds, however, only provide a physical surface treatment to pigment particles and do not bind to the calcium carbonate. Other surface treatments, such as hydrogenated lecithin, will bind to pigment particles, but require water to apply the treatment.
It is desirable to use calcium carbonate as a replacement for titanium dioxide in personal care products. It is further desirable to surface treat calcium carbonate with a hydrophobic compound and develop a method for surface treating calcium carbonate with a hydrophobic compound which does not require significant amounts of water.